This invention relates to an undergravel filtration system for use in aquarium systems. More particularly this invention relates to an improved undergravel filtration system which maintains water in good condition with respect to aeration, cleanliness and removal of toxic waste products.
The maintenance of fish in aquariums for observation is a popular activity. Fish have among the lowest maintenance requirements of any common household pets. They add beauty and tranquility to hotel lobbies, professional offices, restaurants and other environs both public and private.
Fish and other aquarium dwellers are not, however, entirely maintenance free. In order to view the denizens of an aquarium clear water and clean aquarium walls are required. In order to maintain the aquatic animals in good health, well aerated water, free of filth and toxic waste products is necessary.
There are a number of different means of accomplishing this goal. The various methods may be used singly, or in combination. One such means is an undergravel filtration system. Another is a separate filter, in close proximity to the aquarium, through which the aquarium water is filtered.
The undergravel filtration system takes advantage of the layer of gravel, sand, or the like, which is frequently kept at the bottom of an aquarium. This layer of porous material is sometimes colored or sculpted to present a pleasant appearance, discretely catches solid wastes, if particulate, serves as an anchor for some aquatic plants, and mimics a natural environment for bottom feeders.
A typical undergravel filtration system comprises a perforated platform which is placed against the bottom of the aquarium and covered with a gravel layer. A circulation system is attached which allows air to be forced down into the region under the platform and aerate the water it encounters there, the water freely circulating between this space and the habitation area of the aquarium.
The aerated water, after rising through the column and returning to the habitation area of the aquarium, serves as an oxygen source for the aquatic aerobic colonies located in the gravel. Excess air from the water filled habitation area of the aquarium escapes into the surrounding environment.
At the same time, the gravel serves to filter some particulate impurities from the water passing down through it and thus to cleanse and clarify the water. The water is then recirculated to the water filled habitation area of the aquarium. Ideally this is done by returning the water to the aquarium from above the surface of the aquarium, so that additional air is brought into the habitation area.
In my earlier patent, U.S. Pat. No. 5,116,489 I disclosed a reef biological filtration device which drew unfiltered water from the water filled habitation area of an aquarium and returned aerated and filtered water thereto. The water passed upward through a column of stacked large surface area media or bio-balls which served for both filtration and as surface elements for the growth of colonies of aerobic bacteria.
The cultivation of colonies of aerobic bacteria assists in the maintenance of a desirable environment in an aquarium system. Among the waste products of fish and other sizeable aquatic residents is ammonia and other nitrogenous materials. Aquatic aerobic bacteria utilize nitrogenous waste in their nutritional cycle, converting this waste to compounds with a lower degree of toxicity. It is thus desirable to create and maintain colonies of aquatic aerobic bacteria in the aquarium system environment. It is also desirable to do so at a minimal cost, and under conditions which allow for as little maintenance effort as possible.
For healthy growth and maintenance of colonies of aquatic aerobic bacteria a number of conditions must be met. First, sufficient oxygen must be present in the water to meet the needs of the aerobic bacteria, as these organisms not only use oxygen, but also depend upon it. Second, stagnation must be avoided by maintaining water flow, usually by circulation. Aquatic aerobic bacteria depend on water flow to transport the required oxygen to their colonies, and stagnation means oxygen starvation. Third, the water must be channeled so that there are no regions which are not exposed to aerated water. The creation of such non-aerated regions or dead spaces has a deleterious effect on the system because anaerobic bacteria are encouraged to grow in dead spaces. Anaerobic bacteria produce wastes that are toxic to aquatic animals and hence are hazardous to them. Fourth, a large surface area media is desirable as colonies of aerobic bacteria tend to attach themselves to exposed surfaces and, under favorable conditions, the larger the surface area the more colonies of aerobic bacteria that can be maintained.
Unfortunately, the last two requirements are not inherently mutually compatible. Thus, for example, gravel can be made to have a larger and larger surface area by breaking it up into successively smaller pieces. When gravel or sand becomes extremely fine, however, it becomes extremely difficult to maintain water flow in a uniform and efficient mode, to prevent channeling, and to keep the media functionally clean.
Keeping the media clean is necessary for both the appearance of the system and the health of the aquatic life. However, cleaning presents a problem. When filters are back-flushed or otherwise cleaned, most of the colonies of aquatic aerobic bacteria are destroyed in the process. Although sufficient aerobic bacteria generally remain that the fully active colonies will eventually be reestablished, for some period of time the system must function without the benefit of thriving colonies of aquatic aerobic bacteria. Because of this hiatus, the aquatic animals are exposed to unhealthy conditions, and the environment of the aquarium system disintegrates more rapidly so that more frequent maintenance is necessary.